The term Workability of concrete is used to describe the ease or difficulty with which the concrete is handled, transported and placed .The loss of homogeneity is minimum.
As a physical property of concrete can be defined as amount of useful work done to produce full compaction.
Workability is mainly affected on following reasons:
- Water content,water cement ratio and aggregate cement ratio.
- Grading,shape,texture and maximum size of coarse aggregate used in mixture.
The concrete mixture for one work may prove to be too stiff or wet for another work.
The strength of concrete is not to be affected,the degree of workability can be obtained:
- By changing slighty proportions of fine and coarse aggregate in case of concrete mixture is too wet.
- By adding a small quantity of water cement paste in the proportion of mixture.
The workability of concrete is measure by various test but slump test is quite common
SLUMP TEST: In the slump test, standard cone whose length is 300mm,one diameter is 100mm and other diameter is 200mm.
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The concrete is filled about one fourth portionand then rammed
Then it is completely filled with concrete such that cone is full of concrete and then cone is raised vertically and removed.
The concrete is allowed to subside and the height of concrete is measured. The slump is obtained by deducting height of concrete after subside from 30 cm.
The main advantage of slump test is that apparatus is cheap,portable and convenient of same indentical mix.
But major disadvantage is that it is not used for concrete in which maximum size of aggregate exceeds 40mm
Classification of concrete :
Slump nature of concrete mix
No slump stiff and extra stiff mix
10 -20mm poorly mobile mix
40-150mm mobile mix
Over 150mm cast mix
Type of concrete slump
For road construction 20-40mm
For mass concrete 25-50mm
Canal linings 70-80mm
Arch and side walls 90-100mm
Then it is completely filled with concrete such that cone is full of concrete and then cone is raised vertically and removed.
The concrete is allowed to subside and the height of concrete is measured. The slump is obtained by deducting height of concrete after subside from 30 cm.
The main advantage of slump test is that apparatus is cheap,portable and convenient of same indentical mix.
But major disadvantage is that it is not used for concrete in which maximum size of aggregate exceeds 40mm
Classification of concrete :
Slump nature of concrete mix
No slump stiff and extra stiff mix
10 -20mm poorly mobile mix
40-150mm mobile mix
Over 150mm cast mix
Type of concrete slump
For road construction 20-40mm
For mass concrete 25-50mm
Canal linings 70-80mm
Arch and side walls 90-100mm
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